A navigation system performs travel guidance for enabling a user to easily and quickly reach the selected destination. A typical example is a vehicle navigation system where a vehicle is equipped with a GPS (Global Positioning System) navigation function to guide a driver to a destination through a calculated route. Such a navigation system detects the position of the user's vehicle, and reads out map data pertaining to an area at the current vehicle position from a data storage medium, for example, a CD-ROM, a DVD, or a hard disc, etc. of the navigation system, or from a remote data server.
Typically, during a map mode, the navigation system displays a map image on a monitor screen while superimposing thereon a mark representing the current location of the user's vehicle. During a route guidance mode, the navigation system further displays a calculated route to the destination on the map image in a highlighted manner. At an intersection, if a turn is necessary, the navigation system notifies the user which direction to turn at the intersection such as by displaying an arrow image and generating voice instructions.
Today, such navigation systems installed in vehicles have been widely used for route guidance because GPS (Global Positioning System) signals from GPS satellites are available to anyone for detecting an absolute position. Portable navigation devices have also been widely used because of their portability, improved memory capacity, relatively low price, etc. With use of the navigation function incorporated in such a navigation system, it is desirable to achieve new and useful functionalities for expanding applications of the navigation system.